Separator means, particularly a centrifugal separator, also known as a wringer or a centrifuge, are already known for separating mixtures of metal chips from oil, such mixtures being produced for example, by lathes and by other machine tool operations. An example of such a separator is disclosed in U.S. Pat. No. 4,137,176 entitled "Chip Discharge for Continuous Chip Wringer", assigned to the same assignee as is the present disclosure. Another generally similar separator is shown in U.S. Pat. No. 3,850,814. Such separator provides a rotary separator having upwardly diverging sides with a perforate zone intermediate the upper and lower edges thereof. A mixture of chips and oil fed centrally into said rotor moves upwardly along said walls in response to centrifugal force, the oil moving outwardly to suitable receiving means through the perforated zone and the chips doing likewise to other receiving means over the upper edge of said rotor. To assist in conveying the chips to the receiving means for same, said rotor is preferably supplied with impeller means for drawing a strong stream of air into such centrifuge and driving it outwardly with said chips as at least a partial carrier for same.
Such equipment operates very well and has received good commercial acceptance. However, it often happens that bar ends, finished parts or other large pieces of metal are included in the mixture of chips and oil as same is introduced into the separator. If certain ones of the pieces of metal are very large, as they often are, same will seriously damage the rotor of the separator and will often do so very quickly. This has posed a dilemma of either (1) inspecting the mixture prior to introducing same into the separator and removing therefrom such large pieces of metal, which procedure is economically impractical, or (2) submitting to frequent shutdowns and frequent maintenance of the separator as a result of such large pieces of metal entering thereinto. This dilemma has inhibited the commercial acceptance of the separator as above described from what might otherwise be possible.
Attempts to solve the dilemma have been made, such as the provision of an air classification system upstream of the separator to remove the bar ends and other large pieces of metal, but such solutions have not been entirely satisfactory. For example, an air classification system utilized in conjunction with a crusher is shown in a publication of National Conveyors Company, Inc., Bulletin C-1-67, entitled "National ChipVeyors for Metal Chip Processing and Oil Reclamation". This system, however, is very complicated and expensive and therefore has had very limited use in combination with centrifugal separators. The reason is that the potential for severe damage to a separator by large metal pieces is much less than that for a crusher, and therefore the complex and expensive air classification system is harder to justify for a separator than for a crusher.
One workable solution to the dilemma has been developed, is the subject of U.S. Pat. No. 4,310,417, issued Jan. 12, 1982 and is assigned to the same assignee as is the present disclosure. That application discloses the use of an inclined conduit or chute to feed a separator apparatus, which conduit has an opening in the bottom thereof through which a strong current of air is drawn into the conduit and then into the separator, the stream of air being sufficient to entrain chips and liquid in the conduit and carry them to the separator, but being insufficient to entrain large pieces of metal, such that the latter strike a barrier located at the downstream side of the opening and then drop through the opening due to gravity. Despite the advantages of this approach over prior approaches, a problem is still presented when pieces of metal are introduced into the system that are too large to drop through the opening, since those pieces either pass into the separator and cause damage or they become lodged in and obstruct the opening.
Accordingly, the objects of the invention include:
1. To provide inexpensive classification means for removing large pieces of metal from a mixture of such pieces of metal, metal chips and liquid prior to the introduction of the metal chips and liquid into means for separating the liquid and metal chips from each other.
2. To provide inexpensive classification means, as aforesaid, which is compatible with a system in which a large quantity of air is caused to enter into the separating means and expelled therefrom as at least a partial carrier for said chips.
3. To provide inexpensive classification means, as aforesaid, which will be relatively simple and can be applied to equipment of an existing design by relatively minor modification thereof.
4. To provide inexpensive classification means, as aforesaid, which will have a high degree of reliability and will maintain its reliability over a long period of time with a minimum of maintenance.
5. To provide inexpensive classification means, as aforesaid, which will not interfere with the proper operation of the means separating the liquid and chips from each other.